Procedure Produces Sharper AFM Probes

Stephanie Hoeppener is working with an atomic force microscope for which a Jena research team has developed a procedure to produce sharper probes. (Images: Jan-Peter Kasper/University Jena)
AFM is able to scan surfaces so that even tiniest nanostructures become visible. Knowledge about these structures is important, for instance, for the development of new materials and carrier systems for active substances. The size of the probe is highly important for the image quality as it limits the dimensions that can be visualized — the smaller the probe, the smaller the structures that are revealed.

Carbon nanotubes are supposed to be a superior material for the improvement of such scanning probes. However, it is difficult to attach them on scanning probes, which limits their practical use.

Chemists at the university found a way to overcome these problems. The research team of Dr. Ulrich S. Schubert succeeded in developing a process that allows the growth of carbon nanotubes on the actual scanning probe. Schubert is a professor at the university’s Institute of Organic Chemistry and Macromolecular Chemistry.

For the process, the scientists are using microwave radiation for a gentle but rapid growth of the nanotubes. The growth starts at small cobalt particles that are taken up with the help of the AFM tip.
Stephanie Hoeppener from Jena University holds a glass cylinder with carbon nanotubes for atomic force microscopy.
“The metal particles strongly heat up in the microwave and reach a temperature that is sufficient to convert alcohol vapor into carbon. The heating process works in a way similar to that of a forgotten spoon in the kitchen microwave, which also absorbs the microwave radiation very effectively,” explained Tamara Druzhinina from Schubert`s research team. “Carbon nanotubes can be grown very quickly because of the special conditions inside of the microwave which can generate a pressure up to 20 bar,” added her colleague Dr. Stephanie Hoeppener.

“The method we developed can potentially result in a very cost-efficient production technology of, for instance, high resolution probes for scanning force microscopy,” said Schubert. “These are already available on the market but they are very expensive at 350 Euro each. With the process we can reach a price level that also would justify the use of such tips for routine measurements.”